* ntdll.h: Allow usage from plain C code.

	* ntdll.h: Allow usage from plain C code.
	(FSCTL_PIPE_IMPERSONATE): Define.
	(enum _THREAD_INFORMATION_CLASS): Define.
	(RTL_QUERY_REGISTRY_xxx): Define.
	(RTL_REGISTRY_xxx): Define.
	(PRTL_QUERY_REGISTRY_ROUTINE): Define.
	(struct _RTL_QUERY_REGISTRY_TABLE): Define.
	(enum _KEY_VALUE_INFORMATION_CLASS): Define.
	(struct _KEY_VALUE_PARTIAL_INFORMATION): Define.
	(NtAccessCheck): Declare.
	(NtAllocateLocallyUniqueId): Declare.
	(NtCreateKey): Declare.
	(NtDuplicateToken): Declare.
	(NtLoadKey): Declare.
	(NtOpenKey): Declare.
	(NtOpenProcessToken): Declare.
	(NtOpenThreadToken): Declare.
	(NtPrivilegeCheck): Declare.
	(NtQueryInformationToken): Declare.
	(NtQueryValueKey): Declare.
	(NtSetInformationThread): Declare.
	(NtSetInformationToken): Declare.
	(NtSetValueKey): Declare.
	(RtlAbsoluteToSelfRelativeSD): Declare.
	(RtlAddAccessAllowedAce): Declare.
	(RtlAddAccessDeniedAce): Declare.
	(RtlAddAce): Declare.
	(RtlCheckRegistryKey): Declare.
	(RtlCopySid): Declare.
	(RtlCreateAcl): Declare.
	(RtlCreateRegistryKey): Declare.
	(RtlCreateSecurityDescriptor): Declare.
	(RtlEqualPrefixSid): Declare.
	(RtlEqualSid): Declare.
	(RtlFirstFreeAce): Declare.
	(RtlGetAce): Declare.
	(RtlGetDaclSecurityDescriptor): Declare.
	(RtlGetGroupSecurityDescriptor): Declare.
	(RtlGetOwnerSecurityDescriptor): Declare.
	(RtlIdentifierAuthoritySid): Declare.
	(RtlInitializeSid): Declare.
	(RtlLengthSid): Declare.
	(RtlQueryRegistryValues): Declare.
	(RtlSetControlSecurityDescriptor): Declare.
	(RtlSetDaclSecurityDescriptor): Declare.
	(RtlSetGroupSecurityDescriptor): Declare.
	(RtlSetOwnerSecurityDescriptor): Declare.
	(RtlSubAuthorityCountSid): Declare.
	(RtlSubAuthoritySid): Declare.
	(RtlWriteRegistryValue): Declare.